Increment operation in C: double increment in in one expression (C89)

Question

Why the result for the variable c in the following code is -5?

int main()
{
    int a = 2, b = 3, c=0;
    c = b++ - b++ * a; 
    printf("\n%d", c);
    return 0;
}

Also, another question, why d = b++ - b++ is -1 after this one?